St. Leo the Great

Pope from 440 to 461 during the time of the invasion of Attila the Hun. When Attila marched on Rome, Leo went out to meet him and pleaded for leave. As Leo spoke, Attila saw the vision of a man in priestly robes, carrying a bare sword, and threatening to kill the invader if he did not obey Pope Leo. As Leo had a great devotion to Saint Peter, it is generally believed the first pope was the visionary opponent to the Huns. When Genseric invaded Rome, Leo's sanctity and eloquence saved the city again.

Called the Council of Chalcedon to condemn heresies of the day. Fought Nestorianism, Monophysitism, Manichaeism, and Pelagianism. Built churches. Wrote letters and sermons encouraging and teaching his flock, many of which survive today; it is for these writings that Leo was proclaimed a Doctor of the Church in 1574.